`EPS05: Use in-modifier` shouldn't trigger for partial methods where either the declaration or implementation aren't user-controlled

[ZzZombo]

Many source generators use void partial methods w/o explicit access level specified as a programmatic hook for the programmer. In such cases the underlying SG dictates the shape of the method, and there may be no way to influence whether the in modifier is added to the declaration. The reverse situation is also common where the programmer defines the method, and the SG provides an implementation, and it might not support the in modifier, making it a no-op.

But when both parts of the method are directly user controlled it stands to reason that the analyzer should not skip it.